Support for electrodes



April 16, w H. KosAcK SUPPORT FOR ELECTRODES Filed Jan. 26, 1939INVENTOR ///V' .KUS/767K.

ATTO N EY Patented Apr. A16, 1940 UNITED STATES 2,197,526 SUPPORT FonELEo'rRonEs Hans Kosack, Berlin-Steglitz', Germany, assignor to FidesGesellschaft fr die Verwaltung und Verwertung von GewerblichenSchutzrechten mit beschrnkter Haftung, Berlin,Germany, a corporation ofGermany Application January 26, 1939, SerialNo. 252,912 In Germany June10, 1938 13 Claims.

The invention relates to discharge tubes and especially to the supportfor the electrodes of such discharge tubes.

I An object oi the invention is to maintain a fr' iixed distance betweenthe electrode elements, es-

peclaily of the cathode and control electrodes.

Another object of the invention is to provide a support for electrodeswhich will not substantially change in size and form under the influencel of high temperature.

Other objects and advantages of the invention will be apparent from thefollowing description and drawing, in which:

Fig. 1 is a cross-section through a preferred support ior the cathodeand control electrodes.

Figs. 2 and 4 are cross-sections of two modications oi the invention asdisclosed in Fig. 1.

Fig. 3 is a perspective view of an element of Fig. 2.

Fig. 5 is a perspective view of the modification in Fig. i withadditional elements.

Certain types of discharge tubes such as high vacuum amplifier tubesrequire extremely Small distances between individual electrodes,especially the distance between the cathode and the control grid. Thepractical maintaining of such small distances to a constant value isextremely dinicult in tubes of the prior art because such electrodesconsist oi' two separate elements which are fixed' in their positionrelative to one another only at their ends. With such constructions, itis often impossible to maintain the desired narrowtolerances or suchnarrow tolerances are only accomplished at the cost of a great deal oftime and trouble.

The invention provides a construction for the electrodes and electrodesupport in electric dischargetubes whereby the small electrode distancesareuaccurately maintained and the manuiacturi'ng and assembly of theelectrode arrangement is accomplished in a more certain manner.

In particular, a common support of insulating material is used for thetwo or more several electrodes which require small distances between 15them. This common support of insulating material guarantees the accuratemaintaining of the electrode distances at least over the effectivelength of the electrodes and practically over their entire length. Thiscommon insulating support is preferably of ceramic material which notonly has high heat resistance but also will maintain practically itssame size and form under the iniiuence of the high temperatureconstantly present in the tube during operation.

.55 In Fig, l, the support l is of ceramic material and acts as a commonsupport for both the cathode and the grid. This common support in thepreferred embodiment illustrated, has preferably two parallel extendingsurfaces 2 and 3 having the cathode 8 and 9 thereon. This cathode pref-5 erably comprises a base vmetal coating sintered onto the ceramicmaterial as a metal coating. Such a coating may be of platinum, nickel,copper, silver, or other suitable materials. The emitting material isplaced on top o the metal coat- 10 ing and may comprise the familiarelectron emitting barium, strontium and calcium oxide. ,The ceramicmaterial has preferably prolongations i,

5, 6, and l at the corners lateral to the cathode surface. Theseprojections 4, 5, 4(i, and l are pref- 15 erably provided with groovesin which the grid wires are placed. If the grid wires are woundsuificiently tight, an absolutely sure and xed distance between thecathode and grid is assured.

A Suitable heating element I0 is preferably cen-I 20 trally arrangedwithin the ceramic support. This heating element may, of course,comprise the usual heating coil. The heat which is produced in theheating element should be conducted mainly to the emitting surfaces 8and 9 of the cath- 25 ode. The portion of the ceramic Supportadjacentthe projections for the grid wires has means therein which make diicultthe conduction of heat through the ceramic body from the heating elementto' the projections. The means, illus- 30 trated in Fig. 1 by which theheat conduction to the projections is, reduced, are the hollow spaces orcavities II and I2. Y

If several grids are required and accurate spacing is desired, theprojections of the ceramic sup- 35 portmay have slots of diiierentdepths therein. One wire may be wound in slots of one depth and anotherin slots of another depth. For grid wires, molybdenum, iron, nickelalloys, and .the like, may be used. It is desirable, of course, that thewires 40 have an equal expansion to that of the ceramic material.

In order to maintain tight the grid wires id, there is disclosed alaterally inserted exible plate l5 in cross-section in Fig. 2 and inperspective in 45 Fig. 3.

There are, of course, various modiiications that may be made in theembodiment disclosed in Figs.

1 and 2. In Figs. 4 and 5, the projections of the ceramic body IB are soformed that the grid wires 50 lie on the narrow surfaces I'l, I8, I9,and 20, and these surfaces are separated from the main body by deepslots 2l, 22, 23, and 24. These slots have a further advantage in thefact that the vaporized emission material that might be given oi inactivation or subsequentl operation can hardly reach inside these slotsand so there is no danger of forming a conductive layer between thecathode and grid to provide a leak or short circuit between theelectrodes. The surfaces 25, 26, 21, and` 28 between the electrodes maybe covered if desired with substances such as graphite which do not formconducting chemical compounds with the emissive material vaporized onthem. from the electrode. Inserts 3l) and 3| of poorly heat 'con ductingmaterial may be inserted between the heating element 29 and the portionof the insulating body extending towards the grid supporting projectionsI7, IB, I9, and 20. By one or more, or all of these means, the heatproduced by the heatinglk element is conducted, for the -most part, tothe cathode coatings 32 and 33, and the time for heating the cathode tosufcient electron emitting temperature is shorter than it otherwisewould be.

If it should be desired to cool the grid more effectively, cross bands34 and 35 of metal such as copper can be inserted on the ends andcooling vanes 36 and 31 extend therefrom as illustrated in Fig. 5. Amica disc 38, as illustrated also in Fig. 5, serves to support theelectrode arrangement.

The anode preferably consists of a separately supported elementsurrounding the cathode and grid or grids, but itis apparent the controlgrid may be wound on deep slots on the projections and the anodesupported onthe outer ends of these projections.

In fact, various modications may be made in the preferred embodimentillustrated, and accordingly, only such limitations are intended uponthe following claims as is necessitated by the spirit and scope of thefollowing claims.

I claim:

1. An electrode structure for discharge tubes comprising an insulatorhaving a fiat area, a coating of electron emitting material on said flatarea, unitary projections on said insulator and grid wires wound on saidprojections.

2. An electrode struc-ture for discharge tubes comprising an insulatorhaving a flat area, a coating of electron emitting material on said atarea, unitary projections on said insulator and grid wires wound on saidprojections, and heating means for said electron emitting materialenclosed by said insulator.

3. An electrode structure for discharge tubes comprising an insulatorhaving a flat area, a coating of electron emitting material on said flatarea, unitary projections on said insulator and a plurality of gridwires wound in slots of'different depth on said projections.r

4. An electrode structure for discharge tubes comprising an insulatorsubstantially in the form of a polyhedron, a grid wound on saidpolyhedron, a depressed surface on said polyhedron and a coating ofelectron emitting material on said depressed surface.

5. An electrode structure for discharge tubes comprising an insulatorhaving a substantially flat area, electron emitting material on said'flat area, integral insulator projections on at least two sides of saidfiat area and grid wires wound on said projections.

6. An electrode structure for discharge tubes comprising an insulatorhaving a substantially flat area, electron emitting material on saidflat area, integral insulator projections on at least two sides of saidat area and grid wires wound on said projections, and a slot betweensaid projections and the electron emitting material on said flat area.

7. An electrode structure for discharge tubes comprising an insulatorhaving a substantially iiat area, electron emitting material on said atarea, integral projections on at least two sides of said iiat area, gridwires wound on said projections, and a thin wall extending from theportion of the insulator supporting said flat area to the portion of theinsulator supporting said pro- J'ections.

8. An electrode structure for discharge tubes comprising an insulatorhaving a substantially flat area, electron emitting material on saidflat area, integral projections on at least two sides of said flat area,grid wires wound on said projections, and means keeping said grid wirestight.

9. An electrode structure for discharge tubes comprising a ceramicinsulator, grid wires wound on said ceramic insulator, a surface on saidceramic insulator, spaced from said grid wires and a layer of electronemitting material on said surface.

10. An electrode structure for discharge tubes comprising a ceramicinsulator, grid wires wound on said ceramic insulator, a surface on saidin-` sulator spaced from said grid wires, a metal coating bonded to saidsurface and an electron emitting coating on said metal coating.

l1. An electrode support of ceramic material having a flat surface andprojections lateral at an obtuse angle to said surface and havinggrooves in said projections.

12. An electrode support of ceramic material having a iiat surface andprojections lateral of said surface and having grooves therein and aslot between said flat surface and said projections.

13. An electrode structure comprising an insulator member having twoparallel surfaces, electron emitting material on said surfaces,projections lateral of said surfaces and a grid on said projections foreach surface and spaced the same distance therefrom.

HANS KOSACK.

